This invention is an improvement in a rotary/linear fluid actuator, and in particular a compound motion fluid actuator.
The compound motion fluid actuator is a versatile device used in many areas of industry and is capable of producing reciprocal and rotary motion both simultaneously or separately. In industry, a compound motion fluid actuator is often used to perform strenuous tasks at high speeds. One such task is the rapid clamping of assembly line materials. For example, an actuator can be set level with the assembly line work surface during the loading stage of a material. When the material arrives at a desired operation section, the actuator utilizes reciprocal and rotary motion to move up from the work surface, turn into position, and clamp down the work piece so that a desired work operation can be performed on the material on the line. Upon completion of the work operation, the actuator reverses upon which the material is released.
U.S. Pat. No. 3,815,479 to Thompson discloses a design for a compound motion fluid actuator which includes in effect, two separate actuators with a complex coupling mechanism. This is necessary in order to seal the working parts of the rotary actuator from the pressure cavity during reciprocal motion.
In accordance with U.S. Pat. No. 3,815,479, to achieve reciprocal motion, a power cylinder is pressurized on opposite sides of an internal piston. As cylinder pressure increases, so does the internally communicated pressure, causing stress and fatigue on the working parts of the rotary actuator. Another major problem arises when the cylinder bore size increases. As the bore size increases the amount of fluid needed to fill the bore increases. At high speeds, an expensive power unit must be employed to support the necessary fluid flow rates. The result is a costly, bulky device requiring a high fluid flow rate and needing too much space to operate in conjunction with any surrounding equipment.
In accordance with the invention, an actuator can obtain higher clamping forces and speed at lower fluid flow rates, remain relatively small, and reduce internal stress caused by simultaneous reciprocal and rotary motion. In addition, longer extension can be obtained while keeping the fluid pressure flow rate down.